As a stator provided for a motor and a generator used in an electric vehicle, a hybrid vehicle, and the like, there is a split stator made by forming a split stator core member by stacking electromagnetic steel sheets split in a teeth unit and molding an insulator (insulation resin) integrally with the split stator core member. In this kind of the split stator, there is a possibility that cracks and deformation occur in the insulator by the thermal expansion-contraction caused under a usage environment by the difference between the linear expansion coefficients of the insulator and the split stator core member. Then, when the insulator cracked and deformation, the insulation capability of the insulator may be deteriorated, which may cause a short-circuit between the split stator core member and a coil.
Accordingly, there are contemplated various countermeasures for improving the insulation reliability by preventing the insulator from being cracked and deformed. For example, as one of the countermeasures, cracking and deformation of an insulator are prevented by improving the degree of adhesion of the insulator with a split stator core member by forming irregular shapes to side surfaces of a teeth portion of a split stator core member by stacking steel sheets having a different teeth width (Patent Document 1). Further, cracks and deformation of an insulator is prevented by improving the degree of adhesion of the insulator with a core by forming a region whose surface is roughed to a teeth corner in a green compact core molded by press molding magnetic powder (Patent Document 2).